class_docstr: Test the SAFE MTD XML file handler.
class_docstr_tok: ["Test","the","SAFE","MTD","XML","file","handler","."]
docstr: Test the calibration of older data formats (no offset).
docstr_tok: ["Test","the","calibration","of","older","data","formats","(","no","offset",")","."]
code: def test_old_xml_calibration(self):
      """Test the calibration of older data formats (no offset)."""
      fake_data = xr.DataArray(
          [[[0, 1, 2, 3], [4, 1000, 65534, 65535]]],
          dims=["band", "x", "y"],
      )
      result = self.old_xml_fh.calibrate_to_reflectances(
          fake_data, "B01"
      )
      np.testing.assert_allclose(
          result,
          [[[np.nan, 0.01, 0.02, 0.03], [0.04, 10, 655.34, np.inf]]],
      )
  
file_path: satpy/satpy/tests/reader_tests/test_msi_safe.py
imports: import unittest.mock
  from io import BytesIO, StringIO
  import numpy
  import pytest
  import xarray
  from satpy.tests.utils import make_dataid
label_desc: Use image node_id 3 for calling the TestMTDXML obj's underlying member method code with example usage: obj.test_old_xml_calibration() without return types